The present invention relates generally to a suspension system for cables, and more particularly to a system for suspending a paravane or other article from a "mid-span" portion of a cable of an oceanographic seismic cable array.
In oceanographic surveying and other similar operations, a cable array including numerous cables is towed behind a ship or other vessel. The array includes a plurality of laterally-spaced cables to which surveying and other sensing equipment is attached. The cables include fiber-optic or other data conductors, along with load bearing elements sufficient to protect the data conductors from the large loads encountered during towing operations.
In prior systems, to ensure the proper lateral spacing of the cables in the array which often extend for several kilometers, it has heretofore been common to utilize a winch cable, separate from the towed cable array, connected to a paravane or the like. In this prior arrangement, the paravane was also connected to a "tag-line" such as a chain or cable transversely spanning and connected to each of the cables in the towed array. The towed paravane exerted a transverse force, relative to the direction of travel of the towing vessel, on each cable in the array so that the cables were laterally separated from adjacent cables by the tag line.
While this prior arrangement was generally effective, it was also cumbersome to deploy and to retrieve, and obviously required the use of an additional towing or winch line. Often, excessive bending of the towed cable occurred. This excessive bending damaged the fiber-optic or other data carriers in the bent cable. Prior attempts to attach a paravane directly to one of the towed array cables have not been successful. Certain arrangements caused excessive cable bending, while others did not provide a sufficiently secure connection of the paravane to the cable so that the paravane attachment hardware slipped along the outer surface of the cable causing damage thereto. Other paravane attachment hardware exerted excessive radial compressive forces on the cable to which the paravane was attached, thereby damaging the data conductors of the cable.
Therefore, a need has been found for a new and improved suspension system for a seismic cable array for mid-span attachment of a paravane or other article to a cable of a towed cable array.